Mobile terminal with at least two transducers

ABSTRACT

The invention concerns a mobile terminal with at least two transducers (LSm, LSs 1 , LSS 2 ) used simultaneously as loudspeakers for stereophonic effect. According to the invention, one of said transducers is a main transducer (LSm) with a main working frequency band (Bm) corresponding to at least the phone frequency band, while the other transducer is a secondary transducer (LSs 1 ; LSs 2 ) with a secondary working frequency band (Bs 1 ; Bs 2 ) band different from said main frequency band, the lowest frequencies of said secondary working frequency band (Bs 1 ; Bs 2 ) being greater than the lowest frequencies of said main working frequency band.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/309,903 filed Dec. 2, 2011, which is a continuation of U.S. patentapplication Ser. No. 11/336,605 filed Jan. 19, 2006, now U.S. Pat. No.8,094,845, which claims the benefit of priority to European PatentApplication No. 05 300 088.1, filed on Feb. 3, 2005, the contents ofeach being incorporated by reference as if fully set forth herein.

FIELD OF THE INVENTION

The present invention concerns a mobile terminal provided with several(at least two) transducers used as loudspeakers for stereophonic effect.More generally, the invention relates to all mobile apparatus providedwith functionalities to play sound signal (voice signals or melodies),such as mobile phones, or Personal Digital Assistants, or audiorecorders.

BACKGROUND

All existing mobile telephones include a transducer used as an earphonefor listening to the voice of a caller. Some mobile phone are alsoprovided with a transducer used as a loudspeaker for hand-freecommunication. This transducer is generally the same than the one usedas earphone. In both cases, usual transducer works in a standardizedphone frequency band which corresponds to the audio bandwidth of thevoice signal, i.e. between 300 Hz and 3400 Hz, or between 100 Hz and8000 Hz for wide band telephony

More recently, mobile phones used for playing melodies (either ringingmelodies but also all kind of sound signals) have been proposed. In somecases, the same transducer is used as earphone, hand-free loudspeaker,and melody player. However, the useful frequency bandwidth of music isbetween 20 Hz and 20 KHz, which includes the above-mentionedstandardized phone frequency band, but is much greater towards both thelow frequencies and the high frequencies. As a consequence, specifictransducers have been developed in order to obtain a good sound formusic with only one transducer. Generally, these specific transducershave an important size in order to be able to restitute a good sound,especially for the low frequencies.

Now, in order to obtain a stereo effect, it is necessary to provide themobile terminal with at least two transducers used as loudspeakers. Itis already known to provide a mobile phone with two identicaltransducers used as loudspeakers for stereophonic effect, with the sameworking frequency band. However, a compromise has to be made between, onthe one hand, the wish to have a good stereo effect, even for music,and, on the other hand, the bulk constraint. This is especially true inthe domain of the mobile phones wherein the tendency is to miniaturizeas much as possible the total size of the phone while keeping someimportant features such as a large screen and a keypad.

Consequently, known mobile phones do not enable to obtain a goodstereophonic effect for all kind of sound signals, especially for music.

OBJECTS AND SUMMARY

The aim of the invention is to remedy the above drawback by proposing asolution enabling a very good stereophonic effect with a small sizeapparatus.

To this aim, an object of the present invention is to provide a mobileterminal with at least two transducers used simultaneously asloudspeakers for stereophonic effect, characterized in that one of saidtransducers is a main transducer with a main working frequency bandcorresponding to at least the phone frequency band, while the othertransducer is a secondary transducer with a secondary working frequencyband different from said main frequency band, the lowest frequencies ofsaid secondary working frequency band being greater than the lowestfrequencies of said main working frequency band.

In a first embodiment of the invention, said mobile terminal comprisesonly said main transducer and a single secondary transducer, and saidmain working frequency band includes said secondary working frequencyband.

In a second embodiment of the invention said mobile terminal comprisessaid main transducer and at least two secondary transducers withsubstantially identical secondary working bands, and the highestfrequencies of said main working frequency band correspond to the lowestfrequencies of said secondary working frequency band.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention become apparent from thefollowing description of two embodiments of the invention given by wayof non-limiting examples only and with reference to the accompanyingdrawings, in which:

FIG. 1 shows schematically a first embodiment in accordance with theinvention;

FIG. 2 shows the relative positions of the working frequencies bands forthe transducers of the first embodiment;

FIG. 3 shows schematically a second embodiment in accordance with theinvention;

FIG. 4 shows the relative positions of the working frequencies bands forthe transducers of the second embodiment;

FIG. 5a and FIG. 5b a half-part of a housing provided with threetransducers according to the second embodiment of the invention;

FIG. 6 shows a synoptic explaining a possible signal processing for thesecond embodiment.

DETAILED DESCRIPTION

In relation with FIG. 1, which represents a first possible embodimentaccording to the invention, a mobile terminal, for instance a mobilephone, is provided with two transducers used simultaneously asloudspeakers for stereophonic effect. One of the transducers, called inthe following “main transducer” LSm, is chosen in order that its workingfrequency band Bm includes the phone frequency band, which is astandardized band between for instance 300 Hz and 3400 Hz. In theexample of FIG. 2, the lowest frequencies of main working band Bmcorrespond substantially to the lowest frequencies of the phonefrequency band. However, the lowest frequencies may also be less thanthe lowest frequencies of the phone frequency band. The othertransducer, called in the following “secondary transducer” LSs1, ischosen in order that its working frequency band Bs1 is located in theupper part of the frequency spectrum. More precisely, as can be seen inFIG. 2, the lowest frequencies of secondary working band Bs1 are greaterthan the lowest frequencies of said main working frequency band Bm. Inorder to obtain the stereophonic effect with only the two precedingtransducers, main working frequency band Bm also includes the secondaryworking frequency band Bs1.

Tests made by the Applicant with the above embodiment give good resultsfor stereophonic effects, not only for the voice signal, but also formusic, since secondary frequency band Bs1 is chosen at the upper part ofthe frequency spectrum, with higher frequencies which can go up to 20KHz.

In addition, it is not necessary to enlarge the size of the secondarytransducer since its working frequency band is at high frequencies.

In order to reinforce the stereophonic effect, main transducer LSm andsecondary transducer LSs1 are preferably located as far as possible fromeach other. As best shown in FIG. 1, the mobile terminal comprises ahousing 1 of parallelepipedic general form extending along alongitudinal axis 2. It is thus possible to put main transducer LSm andsecondary transducer LSs1 inside said housing 1 as far as possible fromeach other along the direction of said longitudinal axis 2. In thiscase, the user will get a maximum stereophonic effect by putting themobile terminal down on a plane surface so that longitudinal axis 2 isparallel to the plane surface.

Since main frequency band includes at least the phone frequency band,main transducer LPm can also be used for other classical functions of aphone handset, especially as an earphone and/or an hand-freeloudspeaker.

FIGS. 3 and 4 show a second embodiment according to the inventionwherein the mobile terminal is provided with a main transducer LSm andtwo secondary transducers LSs1, LSs2, with substantially identicalsecondary working bands Bs1, Bs2. As in the previous first embodiment,the lowest frequencies of main working band Bm may correspondsubstantially to the lowest frequencies of the phone frequency band, andsecondary working frequency bands Bs1 and Bs2 are located in the upperpart of the frequency spectrum, so that the lowest frequencies ofsecondary working bands Bs1 and Bs2 are greater than the lowestfrequencies of said main working frequency band Bm. However, since thestereophonic effect is mainly due to secondary transducers, it is notnecessary in this embodiment that main band Bm includes also secondarybands Bs1 and Bs2. In a different manner, as can be seen in FIG. 4, thehighest frequencies of said main working frequency band correspond tothe lowest frequencies of said secondary working frequency bands.

In order to reinforce the stereophonic effect, secondary transducersLSs1 and LSs2 are preferably located as far as possible from each other.As best shown in FIG. 3, it is possible to put secondary transducersLSs1 and LSs2 inside housing 1 as far of possible from each other alongthe direction of said longitudinal axis 2. As already mentioned withrespect to first embodiment, the user will get a maximum stereophoniceffect by putting the mobile terminal down on a plane surface so thatlongitudinal axis 2 is parallel to the plane surface.

In addition, since main frequency band Bm corresponds substantially tothe phone frequency band, main transducer LPm can be the transducerclassically used in a phone handset as an earphone and/or an hand-freeloudspeaker.

FIGS. 5a and 5b illustrate a mobile handset provided with threetransducers according to the second embodiment of the invention. Forbetter understanding, the upper half-part of the housing has beenremoved in order to see the inside part of the housing. FIG. 5a showsmain transducer LSm and secondary transducers LSs1 and LSs2 beforeinsertion inside the lower half-part 1′ of the housing, while FIG. 5bshows the same components once inserted inside said lower half part. Oneshould note that secondary transducers LSs1 and LSs2 are smaller thanmain transducer LSm. Accordingly, a good stereophonic effect can beobtained thanks to the invention while keeping in mind the bulkconstraint. As can be seen especially from FIG. 5a , it is generallynecessary to place main transducer LSm inside an airtight cavity 2 inorder to reduce acoustic short-circuits due to a recombination of soundwaves originated from both the rear side and the front side of thetransducer. However, the acoustic short-circuits phenomena is especiallytrue for low frequencies corresponding to low sounds. Since, accordingto the invention, the secondary working frequency bands are chosen inthe upper part of the frequency spectrum, it is not necessary to makeprovision of such airtightness for the secondary transducers.Consequently, secondary transducers can be located advantageously atvery extreme positions inside the housing.

Transducers used as main transducer and secondary transducers can be ofany kind, such as electro-mechanical transducers, or piezo transducers.

In addition to the foregoing features described in relation with FIGS. 1through 5 b, a reinforced stereophonic effect can also be obtained withparticular signal processing of the signals provided to the differenttransducers. FIG. 6 shows a synoptic explaining the signal processingwhich can be made in the case corresponding to the second embodiment. Inthis figure, it is assumed that the sound signal which is to be playedis a stereo signal represented by its right and left channels R and L.However, it must be understood that a better stereophonic effect isobtained even in case the sound signal is not a stereo signal. Bothchannels R and L are classically recombined for delivering to maintransducer LSm. Between the combination means and main transducer LSm, alow pass filter LPF can be introduced. Each of the right and leftchannels are also connected to one of said secondary transducers,respectively LSs1 and LSs2, through high pass band filters HPF. Thecharacteristics of the different filters LPF and HPF will depend on theused transducers but also on the environment of each transducer.Accordingly, high pass filters HPF could be different. The signalsdelivered by said high pass filter can be delivered directly to eachsecondary transducer LSs1 and LSs2. It is also possible to furtherincrease the stereophonic effect by implementing well-knownspatialization algorithms. This is shown on FIG. 6 with reference Spa,consisting in combining on each channel part of the signal taken on theother channel after specific filtering. The above signal processing canalso be adapted for a mobile terminal according to the first embodiment.

What is claimed is:
 1. A wireless transmit/receive unit (WTRU)comprising: a housing extending in a longitudinal direction, extendingin a width direction and extending in a depth direction, the housinghaving at least a first surface extending in the longitudinal and widthdirections and a second surface extending in at least the width anddepth directions, the first surface and the second surface defining aplurality of openings; and first and second transducers operable toreproduce a first audio signal and a second audio signal, respectively,the first transducer configured to operate in a first portion of afrequency band and the second transducer configured to operate in asecond portion of the frequency band, the first and second portions ofthe frequency band overlapping; wherein: the first transducer,positioned in a first part of the housing, is adjacent a first one ofthe openings associated with the first surface and the secondtransducer, positioned in a second part of the housing, is adjacent asecond one of the openings associated with the second surface, the firsttransducer and the second transducer direct sound via the first one ofthe openings and the second one of the openings in different directions,the first transducer and the second transducer are positionedsufficiently remote from each other to reproduce the first audio signaland the second audio signal, as stereophonic sound, the firsttransducer, which is centered in the housing with respect to the widthdirection, is configured to operate as an earphone for handheldcommunication and as a loudspeaker for hand-free communication, and thesecond transducer is offset from a center of the housing with respect tothe width direction.
 2. The WTRU according to claim 1, wherein thesecond transducer is located at one edge within the housing.
 3. The WTRUaccording to claim 1, wherein the first transducer and the secondtransducer are any of: electro-mechanical transducers or piezotransducers.
 4. The WTRU according to claim 1, further comprising atleast one frequency filter configured to filter signals delivered to atleast one of the first transducer or the second transducer.
 5. The WTRUaccording to claim 1, further comprises a frequency spatialization unitconfigured to combine portions of first and second channels to generatethe first and second audio signals.
 6. The WTRU according to claim 1,wherein: the first transducer is configured to receive the first audiosignal, as a first channel of a stereo signal; and the second transduceris configured to receive the second audio signal, as a second channel ofthe stereo signal.
 7. The WTRU of claim 1, further comprising a holdingunit disposed in the housing to hold the first transducer, wherein theholding unit and the first transducer define an air tight cavity.